IIORV EXPEUITIOX — BOTANY. 133 



S/i/a i/ii/its(i, N.A., Hamuicrsley Range; Sida IcpiJa, N.W.A., De Grey 

 River, Gaseoync River; Clavtoiiia sper;^ulari)ia^ Nicliolsou River, Gulf nf Car- 

 pentaria and Capo's River, Queensland. Ptilofiis parvifoliiis extends tD tiie 

 boutiiern cuiifiiies of tlie Central Ereniian rt^gion and crosses into New .South 

 Wales, but is rare in these external areas ; ]h-athyscina Cliaiiibcrsii is kn<j\vn also 

 from IJarrow Range and in N.A. ; Mirbelia oxyc/oJa, Victoria River, Arnlieim 

 Land, Haininersley Range; Biirtoiiia polyzyi^^a, the only external locality is Mount 

 Morpliett on tho confines of Burt Plain ; Swaiusciiia caiiescens is known at two 

 other Idealities, Swan River and Nickol IJay ; Ctissia gii//iiiosa at Attack Creek; 

 Grevilka eriosfacliya, Mui'chison River, Champion J>ay, Nickol River ; Catospcrnia 

 Aliielkn, Victoria River and River Thomson in Queensland. 



From the known habits of the exotic species inhabiting the rocks and pools of 

 the Larapintine gorges and ravine's, it may Ije inferre<l from the circumstance of 

 their local occurrence that they, as well as the Australian species [previously 

 quoted, are on the verge of extinction within the Larapintine area. Tt is 

 satisfactorily established, on geological and biological data, that fiom Pliocene 

 times the rainfall in Central Australia has greatly diminished ; so that, if species 

 of plants were introduced to the region during the duration of the favourable 

 climatic conditions, it is not iinreastjnable to suppose that those less adapted to 

 increasing desiccation would disappear, or continue to live only in those restricted 

 areas where the struggle for existence would l)e the least severe, llence, the 

 deep-shaded gorges and escarpments, particulaily those with perennial wattn'-llows 

 (the rock-structures in the George Gill and Krichaull' Ranges are especially 

 favourable), have become harbours of refuge to the few survivors of an extinct 

 population. 



The most ancient species among the living generation of Australian plant, 

 is Callilris robiisdi, which inhaljitcd Central Austi'alia coeval with the lai-ge e.xtinct 

 marsuj)alia, as they are associated in (he Pliocene clays at Lake Callabonna.* 

 However, the species is absent in a living slate fi-om the Central Eremian regions 

 and does not appear in a northerly direction till the Larapintine table-land is 

 reached. 



The minor inlluences checking reproduction of the species of the endemic 

 flora as conseijueiices of increased aritlity are : — 



(1) The general alisence of perennial streams and the salinity of the surfact; 

 stores of water, which increases \\ith the prolongation of the rainless .season. 



Tatf, Traiis. Hoy. Sue. S. Aiist., vol, wiii., p. li».">, Ib'.n. 



